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SE-1020Dr. Mark L. Hornick
1
The switch statement
int gradeLevel = kbd.nextInt(); // can be byte or short also, but not long
switch( gradeLevel ) { // examine value of gradeLevel
case 1: System.out.print("Go to the Gymnasium"); break;
case 2: System.out.print("Go to the Science Auditorium"); break;
case 3: System.out.print("Go to Harris Hall Rm A3"); break;
case 4: System.out.print("Go to Bolt Hall Rm 101"); break;
}
This statement is executed if the gradeLevel is equal to 1.
This statement is executed if the gradeLevel is equal to 1.
This statement is executed if the gradeLevel is equal to 4.
This statement is executed if the gradeLevel is equal to 4.
SE-1010Dr. Mark L. Hornick
2
The switch statement consists of a switch control expression and one or more case statements
switch ( gradeLevel ) {
case 1: System.out.print( "Go to the Gymnasium" );
break;
case 2: System.out.print( "Go to the Science Auditorium" );
break;
case 3: System.out.print( "Go to Harris Hall Rm A3" );
break;
case 4: System.out.print( "Go to Bolt Hall Rm 101" );
break;
}
Case Body
Case Body
The Switch expression is an arithmetic expression that evaluates to an integer value
The Switch expression is an arithmetic expression that evaluates to an integer value
Case Label
Case Label
ColonColon
SE-1010Dr. Mark L. Hornick
3
The break statements cause the switch to terminate
switch ( N ) {
case 1: x = 10;
break;
case 2: x = 20;
break;
case 3: x = 30;
break;
}
x = 10;x = 10;
false
trueN == 1 ?
N == 1 ?
x = 20;x = 20;
x = 30;x = 30;
N == 2 ?
N == 2 ?
N == 3 ?
N == 3 ?
false
false
true
true
break;break;
break;break;
break;break;
SE-1010Dr. Mark L. Hornick
4
A switch without break statements will not terminate after the case is handled
switch ( N ) {
case 1: x = 10;
case 2: x = 20;
case 3: x = 30;
}
x = 10;x = 10;
false
trueN == 1 ?
N == 1 ?
x = 20;x = 20;
x = 30;x = 30;
N == 2 ?
N == 2 ?
N == 3 ?
N == 3 ?
false
false
true
true
The flow will first start from the matching case body and then proceed to the subsequent case bodies.
SE-1010Dr. Mark L. Hornick
5
the default block handles cases not explicitly handled
switch (ranking) {
case 10:
case 9:
case 8: System.out.print("Master");
break;
case 7:
case 6: System.out.print("Journeyman");
break;
case 5:
case 4: System.out.print("Apprentice");
break;
default: System.out.print("Input error: Invalid Data");
break;
}
SE-1010Dr. Mark L. Hornick
6
The switch expression can also be a char datatype
switch ( ranking ) {
case ‘a’: System.out.print( "Go to the Gymnasium" );
break;
case ‘b’: System.out.print( "Go to the Science Auditorium" );
break;
case ‘c’: System.out.print( "Go to Harris Hall Rm A3" );
break;
case ‘d’: System.out.print( "Go to Bolt Hall Rm 101" );
break;
}
The variable ranking is a char datatype
The variable ranking is a char datatype
